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Pedro -Dawn- · 14-12-2022, 17:51

Hello,

I am building a new panel for my 30gm yanmar engine. I did some research and did not find any simple alternative to replace the Alternator Charge Lamp to an LED. I've explored adding an LED with resistors, but from all threads in forums I could check, this would be at least finicky.

I don't want to gut my existing panel, and for now I would like to keep it as a spare. However, I did not find any specification for the incandescent bulb in the panel (yanmar shop website, etc.). Can anyone point me to the specifics of this lamp?

Also, any wiring pointers here? Do I need to add a blocking diode?

I appreciate any suggestions!!

Cheers

**Wotname** · 14-12-2022, 18:33

It is very easy to do. I have done it in the past and I will dig out the details shortly and post here.

Pedro -Dawn- · 14-12-2022, 18:42

Quote:

Originally Posted by Wotname

It is very easy to do. I have done it in the past and I will dig out the details shortly and post here.

Thank you!!!

**Wotname** · 14-12-2022, 19:04

In essence you electrically replace the existing incandescent charge light with a 47ohm, 5W resistor. Add a 12V* LED in parallel to the resistor to function as the charge light.

Mount resistor wherever convenient and mount the LED in the panel.

*A '12V' LED will have a suitable load resistor built into it however if you just use a 'raw' LED, you need to add a suitable load resistor in series with the LED. The value of the LED load resistor will be determined by the specs of the LED.

jt11791 · 14-12-2022, 19:05

I believe the Yanmar panel uses #555 bulbs. Search that number to find replacements and LED alternatives.

**Wotname** · 14-12-2022, 19:14

Going from memory, I think I determined a 2W resistor would suffice but used a 5W to be well on the safe side. The cost difference was minimal and the physical size difference was not an issue.

The resistor is only passing current when the charge lamp is illuminated.

Pedro -Dawn- · 14-12-2022, 19:34

Quote:

Originally Posted by Wotname

Going from memory, I think I determined a 2W resistor would suffice but used a 5W to be well on the safe side. The cost difference was minimal and the physical size difference was not an issue.

The resistor is only passing current when the charge lamp is illuminated.

Sure thing Wotname!! Can't thank you enough! I am building this new harness on a small bus bar for the "key switch" sources. Should I add an 1amp fuse to this line? Won't this be in excess of the resistor capability?

Sorry if this is a dumb question, I really want to do this, but my knowledge is not there yet...

if I may take a little bit more of your time, should I add blocking diodes to L and R alternators connectors?

Again, thanks!!!

**Wotname** · 15-12-2022, 03:02

Quote:

Originally Posted by Pedro -Dawn-

Sure thing Wotname!! Can't thank you enough! I am building this new harness on a small bus bar for the "key switch" sources. Should I add an 1amp fuse to this line? .........

No, it isn't necessary and it only adds a potential failure point; KISS is best.

Remember the charge light is hardly ever on for more than seconds, a few minutes at the most. The purpose of the charge lamp is twofold. One is obviously that it tells you if the alternator is working (i.e. providing voltage). The other reason is that the current the illuminates the lamp is actually the initial field excitation current. This is the current that excites the field before the alternator rpm is high enough to becomes self sustaining (self exciting). You don't want any potential problem that would interrupt this initial excitation current.

The absolute maximum current through the 47 ohm resistor is 270mA which means the maximum power will be 3.4W.

If you are trying to protect the resistor with a fuse, the numbers become unrealistic. A 5W resistor would need a a maximum fuse of 390mA; a 1A fuse would require 13W resistor; a 500mA fuse would require 7W resistor. The simplest (and best solution) is no fuse and a 5W resistor.

**Wotname** · 15-12-2022, 03:18

Quote:

Originally Posted by Pedro -Dawn-

.........

if I may take a little bit more of your time, should I add blocking diodes to L and R alternators connectors?

Again, thanks!!!

Definitely not, a blocking diode in the R lead will upset internal regulator in the alternator.

The LED in the L lead is a 'blocking diode'. A LED is just a regular diode that emits photons in the visible spectrum. All diodes emit photons but only LEDs emit visible photons.

As you say, your knowledge of the circuity is not there yet so why don't you post a schematic diagram when you get your design worked out and we can give it a quick appraisal. No need to be a fancy drawing, a rough hand drawn 'mud map' will do. No one is born understanding electronics, we all have had to learn it along the way.

Pedro -Dawn- · 15-12-2022, 05:09

Quote:

Originally Posted by Wotname

Definitely not, a blocking diode in the R lead will upset internal regulator in the alternator.

The LED in the L lead is a 'blocking diode'. A LED is just a regular diode that emits photons in the visible spectrum. All diodes emit photons but only LEDs emit visible photons.

As you say, your knowledge of the circuity is not there yet so why don't you post a schematic diagram when you get your design worked out and we can give it a quick appraisal. No need to be a fancy drawing, a rough hand drawn 'mud map' will do. No one is born understanding electronics, we all have had to learn it along the way.

Got you! No fuse and 5W resistor. Makes sense. My inexperience makes me try to fuse every wire hehe.

About the blocking diode, I think some threads in forums discussed how the engine wouldn`t turn off without the diodes.

Here is a sketch of the new harness. The issues I have that motivated me to make a new one are:
- current harness and panel are 30yo and not in great shape, I already redid the whole boat electrical.
- my house and starting battery are far from the engine bay. About a 4m cable run one way. Ideally I should run a 4/0 cable from the battery to the starter (and back from the alternator), however there is no way I can mount a 4/0 cable in the starter studs, right?

About the equipment in the panel?
- The buttons in this drawing are those Halo LED metal buttons, rated for 3A (same as the others in my panel)
- I will buy an LED/buzzer combination for the lights.

As per the sketch, I am considering doing away with the Light Switch and just test the lamps from time to time... Not sure if this is a good idea.

Thank you!!!

Pedro -Dawn- · 15-12-2022, 08:40

Quote:

Originally Posted by Wotname

Definitely not, a blocking diode in the R lead will upset internal regulator in the alternator.

The LED in the L lead is a 'blocking diode'. A LED is just a regular diode that emits photons in the visible spectrum. All diodes emit photons but only LEDs emit visible photons.

As you say, your knowledge of the circuity is not there yet so why don't you post a schematic diagram when you get your design worked out and we can give it a quick appraisal. No need to be a fancy drawing, a rough hand drawn 'mud map' will do. No one is born understanding electronics, we all have had to learn it along the way.

FYI this is the complete diagram for the harness at the moment. Already added your input to it!

**Wotname** · 15-12-2022, 12:54

Quote:

Originally Posted by Pedro -Dawn-

FYI this is the complete diagram for the harness at the moment. Already added your input to it!

I see at least two issues with the this circuit but I don't have time ATM to have a detailed look - sorry.

1. The R wire has to go to the small +ve bus in the control panel as does the +ve side of charge lamp (LED).
2. There is a lack of fusing on a couple of wire - more info when I get more time to look further.

The general thrust of the circuit looks OK, just some detail to attend to

**Wotname** · 15-12-2022, 13:00

Quote:

Originally Posted by Pedro -Dawn-

........
About the blocking diode, I think some threads in forums discussed how the engine wouldn`t turn off without the diodes.
................

The 3GM (and 3GM30) uses a mechanical engine stop cable, nothing electrical about it unless a PO has modified the engine stop arrangement and added a stop solenoid. Even if so, I can't see how the alternator wiring could possibly affect an engine stop solenoid.

BTW, is the engine a 3GM or a 3GM30, not that it matters for the control panel?

**Wotname** · 15-12-2022, 13:33

Quote:

Originally Posted by Pedro -Dawn-

..............
- my house and starting battery are far from the engine bay. About a 4m cable run one way. Ideally I should run a 4/0 cable from the battery to the starter (and back from the alternator), however there is no way I can mount a 4/0 cable in the starter studs, right?.............

4/0 seems overkill, even 2/0 might be overkill but I haven't run numbers ATM. The 3GM doesn't have a high starting current.

If you have to use large cables for a long run, mount a cable stud nearby the engine and terminate the large cable on this stud, then run a short smaller cable from the new stud to the starter motor solenoid.

I note you are connecting the alternator output direct to the house battery, again this certainly does not need a 4/0 cable. What alternator do you have?